Category: Space & Physics

The NASA spacecraft Dawn has spent more than seven years traveling across the solar system to intercept the asteroid Vesta and the dwarf planet Ceres. Now in orbit around Ceres, the probe has returned the first images and data from these distant objects.

But inside Dawn itself is another first – the spacecraft is the first exploratory space mission to use an electrically-powered ion engine rather than conventional rockets.

We all know and love the moon. We’re so assured that we only have one that we don’t even give it a specific name. It is the brightest object in the night sky, and amateur astronomers take great delight in mapping its craters and seas. To date, it is the only other heavenly body with human footprints.

What you might not know is that the moon is not the Earth’s only natural satellite. As recently as 1997, we discovered that another body, 3753 Cruithne, is what’s called a quasi-orbital satellite of Earth. This simply means that Cruithne doesn’t loop around the Earth in a nice ellipse in the same way as the moon, or indeed the artificial satellites we loft into orbit. Instead, Cruithne scuttles around the inner solar system in what’s called a “horseshoe” orbit.

Ceres is the largest object in the asteroid belt, and NASA’s Dawn spacecraft will arrive there on March 6.

Pluto is the largest object in the Kuiper belt, and NASA’s New Horizons spacecraft will arrive there on July 15.

These two events will make 2015 an exciting year for solar system exploration and discovery. But there is much more to this story than mere science. I expect 2015 will be the year when general consensus, built upon our new knowledge of these two objects, will return Pluto and add Ceres to our family of solar system planets.

The efforts of a very small clique of Pluto-haters within the International Astronomical Union (IAU) plutoed Pluto in 2006. Of the approximately 10,000 internationally registered members of the IAU in 2006, only 237 voted in favor of the resolution redefining Pluto as a “dwarf planet” while 157 voted against; the other 9,500 members were not present at the closing session of the IAU General Assembly in Prague at which the vote to demote Pluto was taken. Yet Pluto’s official planetary status was snatched away.

Ceres and Pluto are both spheroidal objects, like Mercury, Earth, Jupiter and Saturn. That’s part of the agreed upon definition of a planet. They both orbit a star, the Sun, like Venus, Mars, Uranus and Neptune. That’s also part of the widely accepted definition of a planet.

I have always been in awe of the night sky, trying to comprehend the vastness of space and the countless wonders it contains. But I have always felt a certain dissatisfaction with only being able to see it at a distance.

One day I imagine that humanity will be able to visit other planets in the solar system, and venture even further to other stars, but this has always seemed very far away. That’s the reason why I applied for the Mars One mission, aimed at starting a human colony on Mars – it seemed like a real opportunity to get closer to the rest of the night sky, to give me a chance to be a part of taking humanity into the stars.

Mars is, in a way, the perfect stepping stone into the rest of the universe. Despite its inhospitable conditions, it has a day-night cycle only 39 minutes longer than on Earth. Unlike the moon, it is resource-rich, and has a soil and atmosphere rich in water and nitrogen respectively. Mars does not suffer from the sweltering heat and toxic atmosphere found on Venus, closer to the sun from Earth, but still receives enough light from the sun to enable the generation of solar power.

I was seduced by infinity at an early age. Georg Cantor’s diagonality proof that some infinities are bigger than others mesmerized me, and his infinite hierarchy of infinities blew my mind. The assumption that something truly infinite exists in nature underlies every physics course I’ve ever taught at MIT—and, indeed, all of modern physics. But it’s an untested assumption, which begs the question: Is it actually true?

The sun sets on the BICEP2 telescope in Antarctica. Credit Steffen Richter, Harvard University

Last week, BICEP2 scientists — who in March announced evidence of cosmic inflation, a potentially Nobel-worthy find — threw handfuls of dust on the grave of their own results. The official paper [pdf], just published on the BICEP website, tells the story of how they mistook cosmic dust for “primordial gravitational waves,” and why everybody needs to calm down and stop trying to bury inflation, too.

What’s inflation?

Just 10-35 seconds after the Big Bang, cosmologists (or at least most of them) believe the universe expanded in hyperdrive — faster than it ever has since and faster than it ever will again. This ballooning, called inflation, smoothed everything out. It turned the cosmos into the roughly homogenous place we see today, and perhaps created other universes that add up to the sci-fi-sounding “multiverse.”

But it’s difficult to find direct evidence that inflation actually happened (after all, it was a long time ago). That’s where B-modes, which the BICEP2 team saw, come in.

This Planck image shows that dust emission is strongest along the plane of the galaxy, in the upper part of the image, but that it cannot be neglected even in other regions of the sky. Credit: ESA/Planck Collaboration

The claim made headlines worldwide, hailing one of the biggest scientific discoveries in decades. After 35 years of research, astronomers said in March, they had found evidence that the universe underwent a brief but ultra-fast expansion when it was roughly a trillionth of a trillionth of a trillionth of a second old. The research team could see a Nobel Prize looming in the distance. So they popped bottles of bubbly in celebration and shared their excitement with the world.

But results confirmed today indicate that the fizz has long gone out of those findings. A second team of astronomers, which includes the initial BICEP2 team itself, used the European Space Agency’s Planck satellite to show that the twisting patterns did not come from the cosmic microwave background at all. They’re nothing but swirling patterns of dust.

“Space, the final frontier,” announces James T. Kirk at the start of the first Star Trek episode. As the spaceship Enterprise flies past the screen, the voice sounds as though it was recorded in a very reverberant cathedral. I know space is a big place, but where are the reflections meant to be coming from? And anyway, space is silent or, to quote the catchy tag line from the 1979 movie Alien, “in space, no one can hear you scream.”

For an astronaut unfortunate enough to be caught outside the spaceship without a space suit, screaming to occupy the moments before asphyxiation would be pointless, as there are no air molecules to carry the sound waves. But Hollywood does not let anything as trivial as physics get in the way of a compelling soundtrack. The latest Star Trek film showed the outside of the soaring Enterprise accompanied by lots of powerful engine noises; the photon torpedoes sounded pretty impressive as well.

Some climatologists argue it may be too late to reverse climate change, and it’s just a matter of time before the Earth becomes uninhabitable – if hundreds of years from now. The recent movie Interstellar raised the notion that we may one day have to escape a dying planet. As astrophysicists and avid science fiction fans, we naturally find the prospect of interstellar colonization intriguing and exciting. But is it practical, or even possible? Or is there a better solution?

Science fiction has painted a certain picture of space travel in popular culture. Drawing on stories of exploration from an age of tall ships, with a good helping of anachronisms and fantastical science, space exploration is often depicted in a romantic style: a crew of human travelers in high-tech ships wandering the galaxy, making discoveries and reporting back home. Perhaps they even find habitable words, some teeming with life (typically humans with different-colored skin), and they trade, colonize, conquer or are conquered. Pretty much, they do as humans have always done since the dawn of their time on Earth.

How closely do these ideas resemble what we may be able to achieve in the next few hundred years? The laws of physics and the principles of engineering will go a long way to helping us answer this question.

The “Pillars of Creation,” a photograph of part of the Eagle Nebula, is one of the most iconic images ever taken by the Hubble telescope. Yesterday, astronomers released a bigger, better, sharper version of the pillars, taken almost two decades after the first.

But an ironic twist – and what we didn’t know twenty years ago – is that the Pillars might have been long ago torn apart by a distant explosion. The photos we snap of them today are high-tech and modern but their subject is clouded by thousands of light-years of remove. Like the post-mortem photography of the Victorian era, the resulting images are lifelike, and beautiful, and sad.